Ethylene–Propylene Segmented Copolymer as an in Situ Compatibilizer for Impact Polypropylene Copolymer: An Assessment of Rheology and Morphology

This work aims to probe the roles of ethylene–propylene segmented copolymer (EPS) in impact polypropylene copolymers (IPCs) by rheological and morphological investigations. A series of IPCs with different EPS contents and molecular structures are prepared by an atmosphere-switching polymerization process (ASPP). The Palierne emulsion model is used to describe the relationship between the rheological response to small amplitude oscillatory deformation and the morphology of IPC. It is found that this model describes well the linear viscoelastic responses of IPC, if the role of EPS is taken into account. An increase in the content of EPS and the length of its PP segments leads to a decrease in the size of the ethylene–propylene random copolymer (EPR) phase domains and the interfacial tension. These results strongly confirm the role of the EPS as a compatibilizer in the IPC system. The adhesion between the PP matrix and the EPR phase domains is enhanced by the presence of the EPS that is produced in situ during the ASPP. For this reason, ASPP is capable of making IPC with an excellent rigidity–toughness balance

Residence Time Distribution in an Asymmetrical Twin-Screw Extruder

Residence time distribution (RTD) is an important parameter for characterizing axial conveying and mixing in a twin-screw extruder (TSE). This work studies the RTD and flow patterns in an asymmetrical TSE (ATSE) using a transparent barrel for visualization. The RTD of an aqueous solution of sodium carboxymethyl cellulose is measured by using red fine sand particles as tracers, collecting them by a moving thin film at the die exit, and counting them for further statistical calculation. The effects of the screw configuration, screw speed, and feed rate are considered. When the geometrical dimensions and operating parameters are identical, the mean residence time t̅ in the ATSE is larger than those in a classical (symmetrical) TSE. This is a signature of backflow occurring in the intermeshing regions through the radial gaps between the low flight and the inner wall of the barrel. It is confirmed by particle image velocimetry. Moreover, a response surface model is developed to quantify the effects of the screw configuration and operating parameters on t̅

Homogeneous Fluidization of Geldart D Particles in a Gas–Solid Fluidized Bed with a Frame Impeller

The influence of agitation of a frame impeller on the fluidization performance of Geldart D particles is experimentally and numerically studied in a gas–solid stirred fluidized bed, using a three-dimensional (3D) unsteady computational fluid dynamics (CFD) simulation. The bed pressure drops obtained from simulations are in reasonable agreement with those measured with pressure transducers, which validates the CFD models. The experimental results of the pressure fluctuation and the simulated ones of the solid volume fraction distribution show that Geldart D particles can perform homogeneous fluidization in the presence of the impeller. The homogeneous fluidization regime expands as the minimum bubbling velocity increases with the agitation speed while the minimum fluidizing velocity remains unaffected. In addition, the uniformity of particle velocities that are distributed in the entire fluidized bed is also improved by the agitation of the frame impeller

Quantum-Chemical Predictions of p<i>K</i>_a’s of Thiols in DMSO

The deprotonation of thiols (on the S–H bond) is widely involved in organic and bio-organic reactions. With the aid of density functional theory (DFT) calculations, the present study focuses on predicting the p<i>K</i>_a’s of thiols. Efforts were first put in searching for an appropriate computational method. To achieve this goal, the accuracy of 13 different DFT functionals (i.e., B3LYP, BB1K, PBE, M06, M05, M06-2X, M06-L, M05-2X, TPSS, MPW1K, MPWB1K, MPW3LYP, TPSSLYP1W) and 6 different total electron basis sets (6-31G­(d), 6-31+G­(d), 6-31+G­(d,p), 6-311+G­(d,p), 6-311++G­(d,p), 6-311++G­(2df,2p)) (with DMSO solvent and SMD solvation model) were examined. The M06-2X/6-311++G­(2df,2p) (M1) method was found to give the best performance in reproducing the reported 16 p<i>K</i>_a’s of thiols, with a standard deviation (SD) of about 0.5 p<i>K</i>_a unit. Meanwhile, the M1 method was found to be excellent in reproducing the gas phase Gibbs free energies of 17 thiols, providing extra evidence for the reliability of the M1 method in treating thiol systems. On this basis, M1 was then used to predict the p<i>K</i>_a’s of 291 thiols whose experimental p<i>K</i>_a values remain unknown. Accordingly, the scope of p<i>K</i>_a’s of different thiols was constructed

Improved Dielectric Properties of Nanocomposites Based on Poly(vinylidene fluoride) and Poly(vinyl alcohol)-Functionalized Graphene

In this work, two series of nanocomposites of poly­(vinylidene fluoride) (PVDF) incorporated with reduced graphene oxide (rGO) and poly­(vinyl alcohol)-modified rGO (rGO-PVA) were fabricated using solution-cast method and their dielectric properties were carefully characterized. Infrared spectroscopy and atom force microscope analysis indicated that PVA chains were successfully grafted onto graphene through ester linkage. The PVA functionalization of graphene surface can not only prevent the agglomeration of original rGO but also enhance the interaction between PVDF and rGO-PVA. Strong hydrogen bonds and charge transfer effect between rGO-PVA and PVDF were determined by infrared and Raman spectroscopies. The dielectric properties of rGO-PVA/PVDF and rGO/PVDF nanocomposites were investigated in a frequency range from 10² Hz to 10⁷ Hz. Both composite systems exhibited an insulator-to-conductor percolating transition as the increase of the filler content. The percolation thresholds were estimated to be 2.24 vol % for rGO-PVA/PVDF composites and 0.61 vol % for rGO/PVDF composites, respectively. Near the percolation threshold, the dielectric permittivity of the nanocomposites was significantly promoted, which can be well explained by interfacial polarization effect and microcapacitor model. Compared to rGO/PVDF composites, higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz. This work provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectric materials

Primers and restriction enzymes used for RFLP analysis of the FcRL3 gene.

<p>Primers and restriction enzymes used for RFLP analysis of the FcRL3 gene.</p

In Situ Raman Spectroscopy Real-Time Monitoring of a Polyester Polymerization Process for Subsequent Process Optimization and Control

Here, in situ Raman spectroscopy is used to develop a method for determining in real time the percentage of esterification denoted as Ester%, a key quality index of polymerization processes in polyester industries. Specifically, Raman spectra of the polymerization (esterification and polyesterification) of terephthalic acid (PTA) and 1,4-butanediol (BDO) to obtain poly(butylene terephthalate) (PBT) are monitored as a function of reaction time. They are processed through a background subtraction algorithm to yield Raman spectra, which allows for the identification and quantification of Raman bands corresponding to the ester and carboxylic groups. The Ester% is calculated by the ratio between the ester and carboxylic groups in terms of the characteristic peak intensities or areas. The ratio based on the Raman peak areas yields more satisfactory results, namely, the calculated values of the Ester% are less noisy and agree better with those obtained by titration. The established in situ Raman spectroscopy method allows for real-time monitoring and quantification of the Ester% during the polymerization process. It will be adopted for process optimization and control at a pilot scale and ultimately at an industrial production scale

Frequencies of alleles and genotypes of FCRL3 polymorphisms in AR patients and controls.

<p>AR, allergic rhinitis; SNP, single-nucleotide polymorphism. Pc: Corrected p value; OR: odds ratios</p><p>Frequencies of alleles and genotypes of FCRL3 polymorphisms in AR patients and controls.</p

FCRL3 gene might be involved into the autoimmunity sensitization phase in the pathogenesis of AR.

<p>PC: plasma cell, MC: mast cell, Eos: eosinophilic granulocyte.</p